Paragonite-chloritoid alteration in the Trafalgar Fault and Fimiston- and Oroya-style gold lodes in the Paringa South mine, Golden Mile, Kalgoorlie: 2. Muscovite-pyrite and silica-chlorite-telluride ore deposited by two superimposed hydrothermal systems

Research output: Contribution to journalArticlepeer-review

7 Citations (Web of Science)

Abstract

The Golden Mile deposit (1751 t Au to 2017) in the Archean Eastern Goldfields Province, Yilgarn Craton, Western Australia, is located in a km-scale envelope of chlorite-calcite-albite alteration overprinting metamorphosed tholeiitic rocks. The propylitic zone (310–340 °C) is centered on D2 strike-slip faults segmenting D1 folds. At the southeast margin of the deposit, 200 m wide hydrolytic paragonite-ankerite-chloritoid alteration (< 0.1 g/t Au) associated with the D2 Trafalgar Fault forms a thermal anomaly (405–425 °C). The Trafalgar alteration zone merges with barren ankerite-sericite replacement in propylitic Paringa Basalt bound to the contact with Golden Mile Dolerite, which extends > 1.5 km northwest to the Paringa South mine. In the mine, D2 faults control Fimiston ore locally overprinted by Oroya ore, whereas D3 reverse faults offsetting the D2-system control only Oroya ore. Representative ore bodies (lodes) were studied by petrographic, geochemical, and thermometric methods. Fimiston ore (4–20 g/t Au) is refractory, characterized by 10% pyrite ± chalcopyrite ± tennantite, and varies in oxidation state (magnetite stable to hematite stable). Gold and tellurides form inclusions in pyrite. In propylitic GMD, lode alteration is zoned from albite stable in veins and selvages (400 °C) to outer hydrolytic phengite-quartz-ankerite replacement (370 °C). The younger Oroya ore in D3 faults contains free gold and is oxidized (5 g/t Au; pyrite-hematite) or reduced (50–120 g/t Au; pyrite-pyrrhotite) close to carbonaceous black schist. Oroya Stage 1 silica-chlorite-siderite replacement (400–425 °C) and As-rich pyrite-arsenopyrite-sphalerite mineralization is crosscut by Stage 2 silica-ankerite fill (385 °C) and Sb-rich pyrite-tetrahedrite-telluride mineralization associated with vanadian muscovite. Mass-balance calculations indicate that the Oroya fluid carried higher concentrations of silica, Fe, V, Ni, and Te than the older Fimiston fluid.

Original languageEnglish
Article numberdoi 10.1007/s00126-018-0813-5
Pages (from-to)697-730
Number of pages34
JournalMineralium Deposita
Volume55
Issue number4
DOIs
Publication statusPublished - 1 Apr 2020

Fingerprint

Dive into the research topics of 'Paragonite-chloritoid alteration in the Trafalgar Fault and Fimiston- and Oroya-style gold lodes in the Paringa South mine, Golden Mile, Kalgoorlie: 2. Muscovite-pyrite and silica-chlorite-telluride ore deposited by two superimposed hydrothermal systems'. Together they form a unique fingerprint.

Cite this